linux-kernel - Re: [PATCH] x86: split e820 reserved entries record to late

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Message-ID: <86802c440808281319i2f727274g505e43a2f6f6cdeb@mail.gmail.com>
Date:	Thu, 28 Aug 2008 13:19:30 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"Linus Torvalds" <torvalds@...ux-foundation.org>,
	"Bjorn Helgaas" <bjorn.helgaas@...com>
Cc:	"Ingo Molnar" <mingo@...e.hu>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Jesse Barnes" <jbarnes@...tuousgeek.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: split e820 reserved entries record to late

On Thu, Aug 28, 2008 at 1:05 PM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
>
> On Thu, 28 Aug 2008, Yinghai Lu wrote:
>>
>> so could let BAR res register at first, or even pnp?
>
> Well, I'm not sure whether PnP or e820 should be first, as long as any
> "real hardware" probing takes precedence over either. I _suspect_ that
> e820 is more trustworthy, which implies that PnP should probably be added
> last. It would be good to have some idea what Windows does, since usually
> all the firmware bugs are essentially hidden by whatever that other OS
> happens to do.
>
> The basic rule really should be: "What do we trust most?" and probe things
> in that order.
>
> So e820 is fairly trustworthy, but we know that it will have various
> random things marked as reserved because they are special in some way (but
> we don't know _how_ they are special - they may well be real BAR's that
> just have a fixed meaning to ACPI or whatever).
>
> But we obviously trust _part_ of it (the RAM stuff) more than we trust
> other parts. So it does make sense to consider that separately.
>
> PnP I personally wouldn't trust at all, except as a way to keep dynamic
> resources away from those things, which is why I'd put it last. But that's
> just my personal gut feeling.
>
> Hardware we generally trust more than any firmware, but even hardware can
> have bugs. And some classes of hardware tends to be less buggy than others
> (ie I'd trust some on-die APIC base pointer before I would trust a Cardbus
> controller BAR, for example).

ok, will move e820_reserve_resource_late to pcibios_resource_survey(),
so it is called vi pci_subsys_init before pnp_system_init

YH
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